Ground loop hell!

[evono]

A while ago I posted about the annoying whine coming from my head-unit. People seemed to think it was a ground loop and after some reasearch im pretty sure thats the problem.
However, I can't get it to go away!
I figured my head-unit had a blown a resister internally (someone mentioned pioneer head units like to do that) so I went ahead a bought the new Pioneer DEH-p4800MP. Wire this baby up and the hum is still there.

Im currently running a single 2006 kicker 750.1 amp. I wired the headunit and sub in myself. Ran the power wires along the left side of the cab and the signal and RCA cables along the right (I heard running them together could cause some noise). Granted I don't have great RCA cables but this is some serious noise to just be minor interfierace.

I can't figure this out anyone have an idea for ways I could either test to make sure it's a ground loop, fix the loop, anything? I want to stick some tweeters in but with this whine its going to sound awful. Thanks in advance

[WeeHooker]

Give us some more details. One or two amps running? # of RCA's out? Locations of AMp(s) Wire gages/ lengths, etc all will help.
As an experiment in the mean time, try:
-adding a GLI ( available from wallmart) to one or both the lines.
- changing/checking your ground including directly to the battery.

[SQnismo]

sounds funny but take some bare wire and wrap some around all of the RCA connections on the back of the HU. then push the RCA wires on so they kinda hold the bare wire on. ive seen alot of people do this on car audio forums and it supposed to work..
ill try and find one of the links in a bit.

[demondrive]

where did you get ground for the deck? nissans dont have a good ground in the harness also did you get a GOOD ground for your amp? aaaalso make sure your battery terminals are good and clean (no corrosion)

[evono]

Well I have two amps and on further inspection, I belive the sub is not making this sound however 2 sony speakers I have running off a separate amp are still whining. LOUDLY

I tried ground the preouts... I do that with all pioneer HUs they blow connections too easily. Battery was replaced not long ago but I still went ahead and ran a steel brush over the terminals. They are clean
Headunit is seperatly grounded to a screw behind the dash that i'm 99% sure is a good ground.

Amps are grounded to the same screw could this be an issue (they have seperate positve lines with different fuses)

I'v just heard of a grounding kit... despite no one being sure if it actually helps performance could that possibly fix the problem? makes sense...

[demondrive]

well the reason the sub isnt making this sound is because subs souldnt be making anythin in the higher frequency range, b/c of either the amp (if its set right) deck (if its on sub out) and just the way the sub works, what guage power and ground wires are you using? you shoud run one 4guage to a distribution block then split that to go to each amp, and make sure wherever you have the grounds for the amp, its clean of paint and use a star washer that will "bite" into the metal. they also make double shielded rcas (bestbuy about 15 bucks) that help reduce noise, and they make noise filters you can install, but typically if everything is done right it should be fine without that, take it to a bestbuy or circuit city and see if they can help ya, if they are cool (like me! =P) they will at least take a look at your grounds for you to make sure they are good

BTW ive had 3 pioneers and never ever ever needed to "ground" the preouts. if you can, take pics of your grounds ( for deck AND subs)

[tech12volt]

Originally Posted by SQnismo

sounds funny but take some bare wire and wrap some around all of the RCA connections on the back of the HU. then push the RCA wires on so they kinda hold the bare wire on. ive seen alot of people do this on car audio forums and it supposed to work..
ill try and find one of the links in a bit.

Pioneer is afmous for this since they switched from mosfet to jfet power supplies. But the wire trick should work. Try the sub rcas first !!

[SQnismo]

^^ and thats why i now have an Eclipse.

[demondrive]

when did they switch? i havnt used many older pioneer decks but ive had 3 over the last 3 years and they have all been good ( and as far as i remember mosfet)

[Mylt1]

not sure when they switched but almost every forum im on that has an audio section has had the same problem listed time and time again. which is why i will not use pioneer decks.